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The difference beteeen calls

importance: 5

Let’s create a new rabbit object:

function Rabbit(name) {
  this.name = name;
}
Rabbit.prototype.sayHi = function() {
  alert(this.name);
};

let rabbit = new Rabbit("Rabbit");

These calls do the same thing or not?

rabbit.sayHi();
Rabbit.prototype.sayHi();
Object.getPrototypeOf(rabbit).sayHi();
rabbit.__proto__.sayHi();

The first call has this == rabbit, the other ones have this equal to Rabbit.prototype, because it’s actually the object before the dot.

So only the first call shows Rabbit, other ones show undefined:

function Rabbit(name) {
  this.name = name;
}
Rabbit.prototype.sayHi = function() {
  alert( this.name );
}

let rabbit = new Rabbit("Rabbit");

rabbit.sayHi();                        // Rabbit
Rabbit.prototype.sayHi();              // undefined
Object.getPrototypeOf(rabbit).sayHi(); // undefined
rabbit.__proto__.sayHi();              // undefined